Apparatus for continuously measuring denier and denier variability of a substantially constant elastic modulus elastomeric yarn



May 18, 1965 w, DUNCAN 3,183,711

APPARATUS FOR CONTINUOUSLY MEASURING DENIER AND DENIER VARIABILITY OF A SUBSTANTIALLY CONSTANT ELASTIC MODULUS ELASTOMERIC YARN Filed June 13, 1962 v PACKAGE '2' I 2 FEED ROLL S ELONGATION 40 PNEUMATIC 90$ DISPOSAL JET PINcI-I ROLL I 6 (RUBBER COVERED) POLYURETHANE FOAM (VIBRATION ISOLATION) CHOPPER STABILIZED AMPLIEI R L456 VOLTAGE TO FREQUENCY CON vERr R 38 COUNTER /cON TROLLER 4O INVENTOR Ml Z/AM lA/VKFMD Du/I/CA/V DIGITAL PRINTER 42 ATI'ORNEY United States Patent APPARATUS FOR CONTEJUOUSLY MEASURING DENIER AND DENIER VARIABILITY OF A SUB- STANTIALLY CONSTANT ELASTIC MODULUS ELASTOMERIC YARN William Lankford Duncan, Waynesboro, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed June 13, 1962, Ser. No. 202,174 3 Claims. (Cl. 73-160) This invention relates to an improved method and apparatus for determining variations in thickness of thread. More particularly, it relates to an arrangement for continuously measuring the denier and denier variability along the length of an elastomeric yarn of substantially constant elastic modulus.

In the manufacture of elastic yarns and especially synthetic filament yarns of the spandex type, it is highly desirable to check continuously the regularity of the yarn in order to control production and insure perfectly uniform products. Certain variations in denier that occur over distances of several centimeters to several meters of yarn length represent an unacceptable deficiency in spandex yarn production. Therefore, measurement of denier variability is essential in the development of a commercial elastomeric yarn and in maintaining acceptable quality of the product, especially since denier variations in such yarn produce undesirable effects in fabric made therefrom.

In the past it was necessary, in order to determine the periodic variations of yarn denier, to cut the yarn into lengths and weigh the individual segments. This method was time consuming and necessitated the destruction of a certain amount of yarn.

It is an important object of this invention to provide a testing device that measures the variations in denier of a traveling yarn as the yarn passes a given point, without the necessity of significantly affecting, consuming, or destroying the yarn.

Another object is the provision of an arrangement to detect irregularities in elastic filamentary material in a quick and economical, yet reliable, manner.

A further object is to provide a process and apparatus for measuring average denier as Well as variations in denier of a spandex yarn without altering any of its physical properties, which apparatus includes means for indicating and/or recording the amount of denier variation instrumentally.

These and other objects are accomplished by an arrangement for measuring variation in denier of a bare elastomeric yarn in which:

(1) The yarn is advanced to a first zone under substantially no tension,

(2) The yarn is elongated a constant amount of at least in said first zone,

(3) The yarn is advanced to a second zone and elongated a constant additional amount of at least 25% in said second zone, said elongations in said first and second zones being based on the original untensioned length of said yarn,

(4) The yarn is advanced to a third zone and elongated in said third zone an additional amount equal to at least of the amount of elongation effected in said second zone, and

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(5 Variations in tension of the yarn are detected in said second zone and a signal produced corresponding to the nature and amount of the variation.

The invention is illustrated in the figure which shows a somewhat schematic view in perspective of one arrangement for carrying out the process of the invention.

In the figure a feed roll 10 driven by means, not shown, bears against a yarn supply bobbin or package 12. As said roll 10 rotates, the yarn 14 unwinds from package 12, passing across the surface of the roll 10 at substantially no tension. Yarn 14 is subjected to an elongation amounting to 10% of its unstretched length by advancing rolls 1'6 and 18 which are driven by synchronous motors at a rate which is 5% and 10% greater, respectively, than the rate of rotation of feed roll 10. In the next zone lying between advancing rolls 18 and 20, the yarn is elongated an additional 40% by the increased speed of rotation of roll 20*, also driven by a synchronous motor. Finally, in the third zone, the yarn is stretched an additional 5% by advancing roll 22 driven by synchronous motor at a speed 55% greater than that of roll 10. After passing between pinch roll 24 and roll 22, the yarn is" then removed from the testing apparatus by pneumatic jet 26.

Engaging the yarn in the second zone between advancing rolls 18 and 20 is a pulley 28 connected to a strain gage 30 immersed in a block of foam or other cushioning material 32. Variations in the tension of the yarn passing between rolls 18 and 20 are detected by vertical movement of pulley 23 and are transmitted mechanically to strain gage 30, electrically powered by a suitable supply unit 34. The strain gage contains a transducer, not shown, as sensing element. The voltage output signal generated by the transducer is suitably amplied by unit 34 and fed to the input of an electronic integrator consisting of a resistance-capacitance coupling network 36 designed to remove the average denier component voltage and pass only the denier variation component voltage of the signal. Output from unit 36 is fed to a voltage-to-frequency converter 38, which converts the denier variation analog voltage to a pulse rate signal proportional to denier variation. These pulses are accumulated, or counted, by an electronic timer/counter 40, which displays a numerical count equivalent to the time integral of the denier variations. The displayed count may be recorded by printing unit 42 and by suitable calibration is interpretable as the mean deviation in denier of yarn 14.

This invention is useful in the characterization of bare elastomeric yarn. By elastomeric yarn is meant a continuous monofilament or coalesced multifilament having an elongationat break greater than and exhibiting substantially complete recovery from 100% elongation. By bare yarn is meant a yarn having no covering of other fibers wrapped or twisted thereabout. A particularly satisfactory class of elastomeric yarns which are quite useful in the bare or uncovered state is known as spandex. Spandex is used herein in its generic sense to mean yarns formed of manufactured fibers in which at least 35% of the fiber-forming substance is a segmented.

polyurethane. Segmented polymers of this general type are known in the art, for example as disclosed in US.

Patents 2,929,801; 2,929,802; 2,929,803; 2,929,804; 2,95 3,--

839; 2,957,852; 2,962,470; and 2,999,839. Many of the segmented polymers of this type when in the form of a e3 monofilament or coalesced multifilament have elongations at break greater than 100%, tensile recoveries of over 90%, and stress decays less than 20%, as defined in US. 2,957,852.

The first step in the process of this invention is the forwarding of the elastic yarn to the first zone under substantially no tension. This may be done by various catenary arrangements but is preferably accomplished by the process of print unwinding of an already formed package'or bobbin of yarn Wound under very low but uniform tension. Print unwinding involves driving the supply package by a roll which is in frictional driving contact with the surface of the package, and positioning 'It follows that under the constant elastic modulus and constant elongation conditions of this invention, tension the driven package on the periphery of the roll so that V the unwinding yarn line from the package passes around the periphery of the roll for at least 60 of are.

On leaving the feed roll in a print unwinding arrangement, the yarn enters a first stretch zone. A minimum elongation of 5% must be eifected in this zone. Preferably, an elongation of is carried out in this Zone in two increments of 5% each. It has been found that when the elongation in this zone is carried out in a single step, such elongation should not exceed 10%. gation is carried out in a plurality ofsteps, a total elongation in the first zone may, if desired, run as high as but ordinarily should not exceed 50%. It is to be understood that throughout this specification, unless otherwise indicated, the elongations of the elastomeric yarn are related to the original length of the yarn under no tension. Thus, two successive elongations of 5% each are additive, and the total elongation of the yarn after such treatment is correctly expressed as 10%.

On leaving the first zone, the yarn, having been elongated in an amount of between 5% and 50% of its original length, then passes to the second, or measuring, zone. For effective practice of this invention, the additional elongation which the yarn undergoes in the second zone should be in the range of from 25% to about 70%. The total elongation -in;the first and second zones is therefore at least'30%. Preferably, the total elongation in the first and second Zones taken together is 50%. This total elongation should not exceed 75%, since it has been found given to the yarn is not as critical as in the other two.

zones. However, an elongation of at least 10% of the amount of elongation in the second zone should be 'im posed on the yarn in the third zone. Thus, at the minimum elongation of 25% in the second zone, the elongation in the third zone must be at least an additional 2.5%. Preferably in the third zone, an additional 5% to 10% of actual elongation is imposed.

After leaving the third zone, theyarn may then be disposed of in any convenient manner. It may be rewound for further use, or it may be advanced directly'to knitting machines or looms for suitable fabricatiomior it may be discarded, as desired.

The use of a series of rolls driven by synchronous motors, not shown in the drawing, is the preferred method of operation. This arrangement affords simplicity, flexibility, and ease of string-up. Alternate arrangements involve the use of a stepped'pulley and idler rolls :to give the required zones of elongation in the practice of this invention.

If the elonis a function of cross-sectional area and hence of denier.

For the accurate practice of this invention, it is essential that the amount of elongation of the yarn be precisely controlled. It is, therefore, of great importance that there be no slippage or creeping of the yarn in the zonewherein measurement of tension is made. This is the primary purpose of tensioning the yarn in the first zone (pretensioning) and tensioning the yarn in the third zone (post-tensioning), rather than conducting the elongation and tension measurement in a single zone.

The present invention affords the important advantage of reduced time and expense in analyzing elastic yarns for denier uniformity. Yarn is easily processed by the present invention at speeds of 25 meters per minute on a continuous basis.

While one preferred version of an arrangement embodying the present invention has been disclosed and described in accordance with the patent laws, it is recognized that a number of modifications within the spirit of the invention will occur to those skilled in the art. All such modifications are intended to fall within the scope of the following claims.

I claim:

1. An apparatus for continuously sensing and indicating the denier of a moving elastic yarn line of substantially constant elastic modulus, said apparatus comprising in combination a first means for engaging and advancing an elastic yarn line from a supply point to a first zone while in a condition of substantially zero yarn tension, a second means engaging the yarn line for advancing said yarn line through said first zone while elongating the yarn line without slippage a given constant amount between about ,I 5% and about 10%, a third means engaging said yarn line for advancing said yarn line from said first Zone through a. second zone While additionally elongating the yarn line without slippage a given constant amount between about 25% and about a fourth means engaging said yarn line for advancing said yarn line from said second zone through a third zone while additionally elongating the yarn line without slippage a given constant amount between about 2.5% and about 10%; a fifth means for removing said yarn line from said third zone, and a sixth means cooperating said yarn line in said second zone for continuously measuring and indicating the denier of said yarn line, said sixth means comprising a unit engaging and deflecting said yarn line, in said second zone, from its normal path a given amount with a given force, said unit constructed and arranged to detect variations in the force required to maintain the yarn line in the deflected path, said unit producing a signal corresponding to variations in force, said unit cooperating with an indicating means such that said signal actuates said indicating means to indicate continuously variations in denier of said yarn line.

2. The apparatus of claim 1 in which said unit is provided with 'a mounting arrangement for substantially isolating said unit from all variable forces except those applied by said deflected yarn line.

3. An apparatus for continuously sensing and indicating the; denier of a moving elastic yarn line of substantially constant elastic modulus, said apparatus comprising in combination a first means for engaging and advancing an 'In the preferred arrangement as shown in the drawing,

the yarn is removed from a package by printunwinding.

Then by passage over a set of rolls, driven at speeds synchronized with the feed roll, the yarn is elongated Without slippage so that the tension of the yarn at elongation maybe continuously. measured and recorded;

According to Ho0kes law, str'ess is proportional to strain.

second zone while additionally elongating the yarn line without slippage a given'constant amount between about 25% and about 70%, a fourth means engaging said yarn 1 line for advancing said yarn line from said second zone through a third zone while additionally elongating the yarn line without slippage a given constant amount between about 2.5% and about 10%, and an additional means cooperating said yarn line in said second zone for continuously measuring and indicating the denier of said yarn line, said additional means comprising a unit engaging and deflecting said yarn line, in said second zone, from its normal path a given amount with a given force, said unit constructed and arranged to detect variations in the force required to maintain the yarn line in the deflected path, said unit producing a signal corresponding to varia- 6 tions in force, said unit cooperating with an indicating means such that said signal actuates said indicating means to indicate continuously variations in denier of said yarn line.

References Cited by the Examiner UNITED STATES PATENTS 2,844,028 7/58 Benn 73-16O RICHARD C. QUEISSER, Primary Examiner.

ROBERT EVANS, Examiner. 

1. APPARATUS FOR CONTINUOUSLY SENSING AND INDICATING THE DENIER OF A MOVING ELASTIC YARN LINE OF SUBSTANTIALLY CONSTANT ELASTIC MODULUS, SAID APPARATUS COMPRISING IN COMBINATION A FIRST MEANS FOR ENGAGING AND ADVANCING AN ELASTIC YARN LINE FROM A SUPPLY POINT TO A FIRST ZONE WHILE IN A CONDITION OF SUBSTANTIALLY ZERO YARN TENSION, A SECOND MEANS ENGAGING THE YARN LINE FOR ADVANCING SAID YARN LINE THROUGH SAID FIRST ZONE WHILE ELONGATING THE YARN LINE WITHOUT SLIPPAGE A GIVEN CONSTANT AMOUNT BETWEEN ABOUT 5% AND ABOUT 10%, A THIRD MEANS ENGAGING SAID YARN LINE FOR ADVANCING SAID YARN LINE FROM SAID FIRST ZONE THROUGH A SECOND ZONE WHILE ADDITIONALLY ELONGATING THE YARN LIKE WITHOUT SLIPPAGE A GIVEN CONSTANT AMOUNT BETWEEN ABOUT 25% AND ABOUT 70%, A FOURTH MEANS ENGAGING SAID YARN FOR ADVANCING SAID YARN LINE FROM SAID SECOND ZONE THROUGH A THIRD ZONE WHILE ADDITIONALLY ELONGATING THE YARN LINE WITHOUT SLIPPAGE A GIVEN CONSTANT AMOUNT BETWEEN ABOUT 2.5% IN ABOUT 10%, A FIFTH MEANS FOR REMOVING SAID YARN LIKE FROM SAID THIRD ZONE, AND A SIXTH MEANS COOPERATING SAID YARN LINE IN SAID SECOND ZONE FOR CONTINUOUSLY MEASURING AND INDICATING THE DENIER OF SAID YARN LINE, SAID SIXTH MEANS COMPRISING A UNIT ENGAGING AND DEFLECTING SAID YARN LINE, IN SAID SECOND ZONE, FROM ITS NORMAL PATH A GIVEN AMOUNT WITH A GIVEN FORCE, SAID UNIT CONSTRUCTED AND ARRANGED TO DETECT VARIATIONS IN THE FORCE REQUIRED TO MAINTAIN THE YARN LINE IN THE DEFLECTED PATH, SAID UNIT PRODUCING A SIGNAL CORRESPONDING TO VARIATIONS IN FORCE, SAID UNIT COOPERATING WITH AN INDICATING MEANS SUCH THAT SAID SIGNAL ACTUATES SAID INDICATING MEANS TO INDICATE CONTINUOUSLY VARIATIONS IN DENIER OF SAID YARN LINE. 